Underground water distribution systems for residential and commercial areas often incorporate low flow or dead end portions by design. For instance, fire protection and land development codes often require oversized water mains for anticipated fire control and peak water demands. Such design features, although in the best interest of the community, have the effect of dramatically reducing water flow velocity and potentially increasing instances of poor water quality areas within a water distribution system. The problem is further exacerbated by water distribution systems that experience large seasonal fluctuations in demand. These systems often experience additional reduction in water flow during non-seasonal periods of the year.
Low water flow conditions and corresponding increases in water retention time within portions of the water distribution system have the potential to degrade the chemical and microbiological quality of water transported through the distribution system. Degradation in water quality can result from prolonged exposure to water system materials, internal sedimentation, and/or contaminant deposits within a piping system. Disinfectants are commonly used in an effort to control bacterial growth. However, as disinfectant residuals dissipate, bacterial regrowth occurs.
In the United States, the Environmental Protection Agency (EPA) sets standards for tap water and public water systems under the Safe Drinking Water Act (SDWA). The SDWA requires that potable, or drinkable, water systems maintain minimum disinfectant residual levels, to prevent the regrowth of bacteria. Mandatory testing programs exist to track compliance and identify potential health hazards. Water systems failing to adhere to regulatory or operational water quality standards are subject to regulatory enforcement action, public disclosure of health hazards, and increased public and regulatory scrutiny.
Additionally, corrosion rates in low flow and stagnant areas can escalate as chemical reactions and microbiological activity increase. Corrosive water tends to dissolve certain materials commonly used in the construction of water distribution systems. The two primary metals of concern are iron and lead. Iron is commonly found in piping system materials. Lead is commonly found in older water systems that have incorporated lead joints, lead composite pipes and/or brass fittings. Elevated iron concentrations can result in violations of drinking water standards. In both potable and non-potable water distribution systems, excessive concentrations of iron can result in staining of structure surfaces, fixtures and clothing.
Water distribution system compliance with water quality regulatory standards can be evaluated through the collection and analysis of water samples. Samples can be collected from plumbing systems and stationary water sampling stations installed within a water system distribution system. These designated sampling locations often produce test results that are either inaccurate or not representative of water quality throughout the water distribution system. Furthermore, collected data is only useful if it can be evaluated promptly. When human resources are required for such evaluations, this can lead to increased cost.
One approach to addressing water quality degradation in low flow or dead end areas has been to dispatch workers, on an incidental basis, to manually purge the water from a problem area of a system. This method is contingent on financial and human resource availability.
An approach to supplement manual flushing operations is the monitoring of increased concentrations of disinfectant residuals, in an attempt to counteract the effects of disinfectant residual dissipation, which is a time dependent function of chemical and biological reactions. Using this approach, the disinfectant residual level of the entire system is increased or, alternatively, disinfectant booster stations are positioned at strategic areas along the water distribution system. Disinfectants break down over time and thereby become less effective. Therefore, disinfectant levels must be maintained at appropriate levels. For example, the Federal Safe Drinking Water Act is expected to establish a maximum limit of 4 mg/l for chlorine.
The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. Some of the following measurements are possible in direct contact with a water source in question: temperature, pH, dissolved oxygen, conductivity, Oxygen Reduction potential (ORP), turbidity, Secchi disk depth, requiring direct contact with the water source in question. More complex measurements can sometimes require a lab setting for which a water sample must be collected, preserved, and analyzed at another location. Making these complex measurements can be expensive. Because direct measurements of water quality can be expensive, monitoring programs are typically conducted by government agencies. The cost of implementation of monitoring programs can be reduced by automating sampling and flushing operations. In at least one implementation of the technology, water conditions can be tested or monitored by a programmable apparatus. A programmable apparatus can be configured to receive monitoring and maintenance instructions. Instructions can be input through one or more interfaces via an electronic device in signal communication with a programmable apparatus.
There exist apparatuses capable of analyzing water quality and purging low quality water from low flow or dead end areas of water distribution systems. See for example, U.S. Pat. No. 6,035,704 and U.S. Pat. No. 6,880,556 to Newman, which are fully incorporated by reference herein. These apparatuses provide for the analytical and purging function of the apparatus to be controllable by a remotely operated device. However, the existing apparatuses can be improved upon through better monitoring methods and increased levels of automation within this technology.